576 FXUS63 KIND 271904 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 304 PM EDT Sun Oct 27 2024 .KEY MESSAGES... - Near record warmth Tuesday and Wednesday along with wind gusts of 30 to 40 mph - Rain expected for Halloween, most likely period of rain during the morning to afternoon && .SHORT TERM (This evening through Monday)... Issued at 304 PM EDT Sun Oct 27 2024 Spectacular fall weather continues this afternoon as central Indiana enjoys sunny skies and seasonable temperatures. 18Z temps ranged from the mid 50s to the lower 60s. The surface high will remain as the primary feature influencing weather across the Ohio Valley into Monday. The center of the high will shift east over the next 24 hours which will enable return southerly flow to commence by Monday afternoon. This in tandem with expanding ridging aloft will start the temperature rises that will culminate with near record warming for the forecast area Tuesday and Wednesday. Cloudless skies will continue for the rest of the afternoon and most if not all of tonight with broad subsidence in place across the entire area. RH values have dropped into the 25-35% range this afternoon but the lack of of stronger winds is largely mitigating overall fire danger concerns. Predominant southeast winds will back subtly and diminish to less than 5mph for tonight...setting the stage for another frosty start early Monday over parts of central Indiana. The return flow begins in earnest on Monday with a subtle uptick in moisture advection in advance of a warm front that will lift into the mid Mississippi Valley by the evening. Mid and high clouds will be more prevalent by Monday afternoon and there is even some potential for a bit of diurnal cu as well with the moisture advecting into the area from the southwest. Surface winds will back to southeast by late day in response to the approaching warm front. A tightening pressure gradient will enable some gusts at 15-20mph over the Wabash Valley by mid to late afternoon as well. Temps...nudged low temps down a couple degrees from the blend as ideal radiational cooling conditions in tandem with the antecedent dry conditions...noted by the dewpoints dropping lower than model guidance...will likely enable temps to fall into the lower to mid 30s over much of the forecast area by daybreak Monday. The Indy metro will stay a bit warmer with the light easterly flow bringing modified air off the city. LOw level thermals support highs in the upper 60s and lower 70s for much of the area on Monday. && .LONG TERM (Monday night through Sunday)... Issued at 304 PM EDT Sun Oct 27 2024 The long term period will start off warm and breezy. Broad ridging aloft will become more amplified through midweek while southerly flow at the surface will bring WAA and potentially record breaking warm temperatures. Highs on Tuesday and Wednesday are expected to be in the low 80s. Pressure gradients will tighten up as the ridge amplifies and a trough approaches from the west, leading to a jet setting up to the NW of the area and breezy conditions Tuesday through Thursday. Gusts of around 35 mph will be possible at times for the first few days of the long term, with highest winds expected across the north. Can't quite rule out slightly elevated fire weather conditions for the first few days given how dry the ground is with winds, but Min RH values improving to around 40-50% which should help. A surface low and associated cold front will bring likely showers and thunderstorms on Halloween, with rain moving in from the west during the early morning hours and pushing eastward through the day. Guidance has been pushing up the timing of the rain the last few runs. If that sped up timing comes to fruition, some areas, mainly northwest of I-69, could have the rain end before trick or treating begins. Still not fully confident on when rain comes to an end in regards to trick or treating, but more confident that rain should exit the forecast area by around midnight at the latest per current guidance. Cooler and drier air will settle back in behind the front, leading to highs near 60 again for Friday. Afterwards highs will slowly warm the rest of the weekend with a return to more southerly winds. There will also be a slight chance of rain again over the weekend. && .AVIATION (18Z TAF Issuance)... Issued at 1215 PM EDT Sun Oct 27 2024 Impacts: - None Discussion: VFR conditions will continue through the forecast period as high pressure remains draped across the Ohio Valley. Winds will be primarily from the southeast through the afternoon backing slightly and diminishing tonight under clear skies. The high will shift further east on Monday allowing for return flow from the south to establish and increase over the region. There will be an increase in cirrus with also the potential for at least some diurnal cu as moisture slowly advects into the region. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Ryan LONG TERM...KF AVIATION...Ryan